2014/03/24 13:12:43 -19.769 -70.798 19.7 4.1 Chile
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2014/03/24 13:12:43:0 -19.77 -70.80 19.7 4.1 Chile
Stations used:
C.GO01 CX.PATCX CX.PB01 CX.PB04 CX.PB07 CX.PB11 CX.PB12
CX.PB15 CX.PB16 CX.PSGCX IU.LVC
Filtering commands used:
cut a -30 a 180
rtr
taper w 0.1
hp c 0.02 n 3
lp c 0.06 n 3
Best Fitting Double Couple
Mo = 1.40e+22 dyne-cm
Mw = 4.03
Z = 20 km
Plane Strike Dip Rake
NP1 345 85 -75
NP2 93 16 -161
Principal Axes:
Axis Value Plunge Azimuth
T 1.40e+22 38 62
N 0.00e+00 15 164
P -1.40e+22 48 271
Moment Tensor: (dyne-cm)
Component Value
Mxx 1.96e+21
Mxy 3.70e+21
Mxz 3.13e+21
Myy 3.85e+20
Myz 1.29e+22
Mzz -2.34e+21
--############
-------###############
----------##################
------------##################
---------------###################
----------------####################
------------------########### ######
-------------------########### T #######
--------------------########## #######
--------- ----------####################
--------- P ----------####################
#-------- -----------###################
#----------------------##################-
#----------------------#################
#----------------------################-
##--------------------###############-
##--------------------############--
###------------------###########--
###----------------########---
#####--------------####-----
#########-----##------
############--
Global CMT Convention Moment Tensor:
R T P
-2.34e+21 3.13e+21 -1.29e+22
3.13e+21 1.96e+21 -3.70e+21
-1.29e+22 -3.70e+21 3.85e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20140324131243/index.html
|
STK = 345
DIP = 85
RAKE = -75
MW = 4.03
HS = 20.0
The NDK file is 20140324131243.ndk The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2014/03/24 13:12:43:0 -19.77 -70.80 19.7 4.1 Chile
Stations used:
C.GO01 CX.PATCX CX.PB01 CX.PB04 CX.PB07 CX.PB11 CX.PB12
CX.PB15 CX.PB16 CX.PSGCX IU.LVC
Filtering commands used:
cut a -30 a 180
rtr
taper w 0.1
hp c 0.02 n 3
lp c 0.06 n 3
Best Fitting Double Couple
Mo = 1.40e+22 dyne-cm
Mw = 4.03
Z = 20 km
Plane Strike Dip Rake
NP1 345 85 -75
NP2 93 16 -161
Principal Axes:
Axis Value Plunge Azimuth
T 1.40e+22 38 62
N 0.00e+00 15 164
P -1.40e+22 48 271
Moment Tensor: (dyne-cm)
Component Value
Mxx 1.96e+21
Mxy 3.70e+21
Mxz 3.13e+21
Myy 3.85e+20
Myz 1.29e+22
Mzz -2.34e+21
--############
-------###############
----------##################
------------##################
---------------###################
----------------####################
------------------########### ######
-------------------########### T #######
--------------------########## #######
--------- ----------####################
--------- P ----------####################
#-------- -----------###################
#----------------------##################-
#----------------------#################
#----------------------################-
##--------------------###############-
##--------------------############--
###------------------###########--
###----------------########---
#####--------------####-----
#########-----##------
############--
Global CMT Convention Moment Tensor:
R T P
-2.34e+21 3.13e+21 -1.29e+22
3.13e+21 1.96e+21 -3.70e+21
-1.29e+22 -3.70e+21 3.85e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20140324131243/index.html
|
The focal mechanism was determined using broadband seismic waveforms. The location of the event and the and stations used for the waveform inversion are shown in the next figure.
|
|
|
|
The program wvfgrd96 was used with good traces observed at short distance to determine the focal mechanism, depth and seismic moment. This technique requires a high quality signal and well determined velocity model for the Green functions. To the extent that these are the quality data, this type of mechanism should be preferred over the radiation pattern technique which requires the separate step of defining the pressure and tension quadrants and the correct strike.
The observed and predicted traces are filtered using the following gsac commands:
cut a -30 a 180 rtr taper w 0.1 hp c 0.02 n 3 lp c 0.06 n 3The results of this grid search from 0.5 to 19 km depth are as follow:
DEPTH STK DIP RAKE MW FIT
WVFGRD96 2.0 350 45 -90 3.80 0.4207
WVFGRD96 4.0 350 60 80 3.85 0.2966
WVFGRD96 6.0 345 90 -75 3.86 0.4100
WVFGRD96 8.0 345 90 -80 3.94 0.4971
WVFGRD96 10.0 165 90 75 3.95 0.5879
WVFGRD96 12.0 345 85 -75 3.97 0.6553
WVFGRD96 14.0 345 85 -75 3.99 0.7022
WVFGRD96 16.0 345 85 -75 4.00 0.7333
WVFGRD96 18.0 345 85 -75 4.02 0.7515
WVFGRD96 20.0 345 85 -75 4.03 0.7595
WVFGRD96 22.0 345 85 -75 4.06 0.7588
WVFGRD96 24.0 345 85 -75 4.07 0.7504
WVFGRD96 26.0 165 90 75 4.08 0.7353
WVFGRD96 28.0 345 90 -75 4.09 0.7144
WVFGRD96 30.0 165 85 75 4.10 0.6887
WVFGRD96 32.0 165 80 70 4.10 0.6618
WVFGRD96 34.0 165 75 70 4.11 0.6342
WVFGRD96 36.0 165 75 70 4.12 0.6068
WVFGRD96 38.0 165 75 70 4.12 0.5813
WVFGRD96 40.0 165 85 80 4.26 0.5537
WVFGRD96 42.0 165 80 75 4.26 0.5176
WVFGRD96 44.0 165 80 75 4.26 0.4852
WVFGRD96 46.0 165 75 75 4.27 0.4571
WVFGRD96 48.0 165 75 70 4.27 0.4330
WVFGRD96 50.0 340 40 75 4.32 0.4129
WVFGRD96 52.0 340 40 75 4.33 0.3980
WVFGRD96 54.0 345 35 80 4.33 0.3855
WVFGRD96 56.0 345 35 80 4.34 0.3733
WVFGRD96 58.0 175 55 95 4.34 0.3602
WVFGRD96 60.0 340 35 75 4.35 0.3481
WVFGRD96 62.0 175 60 95 4.35 0.3389
WVFGRD96 64.0 175 60 95 4.36 0.3321
WVFGRD96 66.0 175 60 95 4.36 0.3277
WVFGRD96 68.0 345 30 80 4.37 0.3221
WVFGRD96 70.0 345 30 80 4.37 0.3169
WVFGRD96 72.0 340 30 75 4.38 0.3124
WVFGRD96 74.0 335 30 70 4.38 0.3088
WVFGRD96 76.0 335 30 70 4.38 0.3042
WVFGRD96 78.0 345 25 80 4.39 0.3004
WVFGRD96 80.0 150 60 65 4.37 0.2974
WVFGRD96 82.0 150 60 65 4.37 0.2967
WVFGRD96 84.0 325 60 -80 4.33 0.2955
WVFGRD96 86.0 325 60 -80 4.34 0.3028
WVFGRD96 88.0 325 60 -80 4.34 0.3134
WVFGRD96 90.0 325 60 -80 4.35 0.3227
WVFGRD96 92.0 315 55 -85 4.36 0.3287
WVFGRD96 94.0 315 55 -85 4.37 0.3371
WVFGRD96 96.0 315 55 -85 4.37 0.3432
WVFGRD96 98.0 320 55 -85 4.37 0.3479
WVFGRD96 100.0 320 55 -85 4.38 0.3527
WVFGRD96 102.0 320 55 -85 4.38 0.3574
WVFGRD96 104.0 320 55 -85 4.39 0.3604
WVFGRD96 106.0 135 35 -95 4.39 0.3682
WVFGRD96 108.0 320 55 -85 4.40 0.3717
The best solution is
WVFGRD96 20.0 345 85 -75 4.03 0.7595
The mechanism correspond to the best fit is
|
|
|
The best fit as a function of depth is given in the following figure:
|
|
|
The comparison of the observed and predicted waveforms is given in the next figure. The red traces are the observed and the blue are the predicted. Each observed-predicted component is plotted to the same scale and peak amplitudes are indicated by the numbers to the left of each trace. A pair of numbers is given in black at the right of each predicted traces. The upper number it the time shift required for maximum correlation between the observed and predicted traces. This time shift is required because the synthetics are not computed at exactly the same distance as the observed and because the velocity model used in the predictions may not be perfect. A positive time shift indicates that the prediction is too fast and should be delayed to match the observed trace (shift to the right in this figure). A negative value indicates that the prediction is too slow. The lower number gives the percentage of variance reduction to characterize the individual goodness of fit (100% indicates a perfect fit).
The bandpass filter used in the processing and for the display was
cut a -30 a 180 rtr taper w 0.1 hp c 0.02 n 3 lp c 0.06 n 3
|
|
|
|
| Focal mechanism sensitivity at the preferred depth. The red color indicates a very good fit to thewavefroms. Each solution is plotted as a vector at a given value of strike and dip with the angle of the vector representing the rake angle, measured, with respect to the upward vertical (N) in the figure. |
A check on the assumed source location is possible by looking at the time shifts between the observed and predicted traces. The time shifts for waveform matching arise for several reasons:
Time_shift = A + B cos Azimuth + C Sin Azimuth
The time shifts for this inversion lead to the next figure:
The derived shift in origin time and epicentral coordinates are given at the bottom of the figure.
Thanks also to the many seismic network operators whose dedication make this effort possible: University of Nevada Reno, University of Alaska, University of Washington, Oregon State University, University of Utah, Montana Bureas of Mines, UC Berkely, Caltech, UC San Diego, Saint Louis University, University of Memphis, Lamont Doherty Earth Observatory, the Iris stations and the Transportable Array of EarthScope.
The WUS used for the waveform synthetic seismograms and for the surface wave eigenfunctions and dispersion is as follows:
MODEL.01
Model after 8 iterations
ISOTROPIC
KGS
FLAT EARTH
1-D
CONSTANT VELOCITY
LINE08
LINE09
LINE10
LINE11
H(KM) VP(KM/S) VS(KM/S) RHO(GM/CC) QP QS ETAP ETAS FREFP FREFS
1.9000 3.4065 2.0089 2.2150 0.302E-02 0.679E-02 0.00 0.00 1.00 1.00
6.1000 5.5445 3.2953 2.6089 0.349E-02 0.784E-02 0.00 0.00 1.00 1.00
13.0000 6.2708 3.7396 2.7812 0.212E-02 0.476E-02 0.00 0.00 1.00 1.00
19.0000 6.4075 3.7680 2.8223 0.111E-02 0.249E-02 0.00 0.00 1.00 1.00
0.0000 7.9000 4.6200 3.2760 0.164E-10 0.370E-10 0.00 0.00 1.00 1.00
Here we tabulate the reasons for not using certain digital data sets
The following stations did not have a valid response files: